Radio receiving set



Aug. 13, 1929. WEAVER ET AL RADIO RECEIVING SET Filed Feb. 25, 1925 wfgINVENTORS Waver@ BYj-'L-Zlld @61158 NEY ATTQR Patented Aug. 13, 1929.

"UNITED STATES PATENT QFFICE.

ALLAN VJ'EAVER AND FAY "EAROLD CHASE, 0F BROOKLYN, NEW YRK, .ASSIGNCRSTO AIVIERICAN TE'EPHONE AND TELEGRAPH COMPANY, A. CORPRATION OF NEWYORK.

RADIO RECEIVING SET.

Application led February 25, 199.5.

This invention relutes to rudio receiving Systeme, and more particularlyto receiving circuilc to be used in connection with continuous weveredio telegrephy.

ln rudio telegraph Systeme employing' continuoue weve trnnfnni Sion ithun been the prnctice to receive signals from euch waives by theheterodyne method which involves beetin the received frequency with nlocally generated frequency differing therefrom by un :amount Such an toproduce n bent note which ie audible. lVith this method of reccivii'ig,however, it frequently hnppene that ne nurny ne tive or Six interfering`stationS con be hcurd .eiundtnncouely Where the stutions eignul :it :ifrequency sufficiently clone to the desired frequency to produce nuaudible bent note. in the detector.

One of the objects of the present invention in to provide uy receivingcircuit for coirtinnoue1 weven which will produce audible 'tones in thereceiver without drniendine` upon (the helerodyne principle und whichwill be highly dincriminutive against 'interfering elzriions. Anotherobject of the invention is to provide u, receiving; Set which is inuchmore sensitive to stron-ej signifie than; to week nignuleu Still nnotherobject of the invention in to provide u receivirngr Het eo designed thatthe audible sign-Ll tone heard in the receiver muy be umintnined at uconetant frequency even when receiving' :it very nhort ivztve lengthu.

The invention will non' be incre fully understood from the following'deecription when reed in connection with the uccoinpnnyinn drawing', theligure of 'which Shows n, circuit arrangement embodying,- the principlenof the invention.

itch@rringv to 'the drawing, the receiviire` eet consuete primarily ofn, detector D, :L lowpues filter LPF, u` direct current or louTfrequency uuiplilier LFA, u, source of :rudio 'reqnency current` l), unden rudio freq ueney modulator hh The usual receiving` antenne, All ieprovided, und 'the detector D muy be connected Vto the antenna, throughu high frequency simplifier HFA, if necessary. The high frequencyamplifier Will, of course, be of :my type Well .known in the nrt. AeShown, the high frequency uniplilier HFA is coupled to the uutennnthrough u tuned Serial No. 11,538.

circuit l0, seid circuit being timed to the continuous Wave frequencywhich carries; the signal. The output circuit o f the znnplilier nniy becoupled to the detector l) through n eiinilnr tuned circuit 1l.

The output circuit of the detector D is coupled to the direct currentamplifier LFA through u low-pues filter LPF by ineens of :i highresistance 12. The usuel C battery Il?) provided in the grid circuit ofthe detector to ineke the potential of 'the `grid sufliciently negativewith respect 'to the hlnnient so that during' the spacing intervul (whencontinuous Woven nre not being received) no current will iiow in theplete circuit, und hence no current will flowv through the reeistunce 12due to [he voltage of the l battery 14e. .'Duriiu?)l the niurlriin;linten vul, however, the high frequency oscillations inqiresined upon thegrid will ciusie zt low frequency current to flow from the buttery 141;through the resistance 12, the impulse thus flowing correspondinp` to u,inni-king` current.

',he output circuit of the amplifier LFA ie coupled through a secondreeistnnce 15 to the input circuit of the inodulutiin;1 tube M. A Cbuttery 16 if: coiniectcd in the grid circuit of the amplifier LFA.,During the epocing interval no current is flowing,l through thereeietunce 'l2 from the buttery 14 tlnrt there ie no voltnge drop ncrofathe terminals of renintence 12. Hence the potential of the buttery 1Gshould be euch ne to ineke the grid eullicicnlly negative with respectto the filament duri np,- this interval ibut u, inoxinnnn current willflow from the B buttery 17 through the resistance 15. A C buttery 1S iscleo connected in the grid circuit of the modulator tube M, and thevoltage und polarity of the buttery 18 :ire euch thnt when the vol troeif: nlggebrzlicnlly ud ded to the drop Pf through resistunce 15, thegrid of the 1noduluier tube M will be so nemntive with respect to itslilninent during the spacing; inter-vnl, thut no clflrreru'; cnn flow inite1 output cir cuit even when the alternating voltage from theoecillulor O in also euperposed on the grid A telephone receiver R ,inconnected in the plete circuit in series with the B buttery 1%.), undduring the nnrrlringinter vnl. the voltage upon the grid of theinoduluthe Afilament to the plate.

`can flow in the outward circuit.

tor tube will be made less negative in a manner `to be hereinafterdescribed, so that a pulsating wave of the frequency of the oscillator Owill be produced in the receiver ll. The audio frequency source O may beof any type well known in the art but illustrated as a simple tubeoscillator circuit generating an audible frequency of, say, SOCI cyclesper second. y

The operation is as follows: Interrupted continuous frequency waves arereceived. upon the antenna AR andl are amplified by the highfrequency'amplifier HFA and then impressed' upon the grid circuit of thedetector D. During the spacing intervals no high frequency oscillationsare received. During this interval the grid is rendered suficientlynegative due to the voltage of the battery 13, so that no electrons canpass from y Consequently no current flows from the B battery 14 throughthe coupling resistance 12. Therefore the 1R drop across the terminalsof the resistance 12 is Zero, and 'hence the dierence in potenf' tialbetween the grid of the amplifier LFA and the filament of said amplifieris 'that due to the C battery 1G. This battery is so proportioned as tomake the grid just sulliciently negative with respect to the filament sothat a desired maximum current will ilow in the plate circuit'during thespacing interval The large current thus flowing from the battery 17through the resistance 15 causes a considerable IR drop through saidresistance, and this drop, when algeoraically added to the potential ofthe battery 1S will render the grid of the modulator tube M so negativeWith respect to its filament that no current ln other words, the gridisso negative that the tube is operating well along the flat Zero partof its characteristic curve, and the variation in potential ofthe griddue to the oscillations from the oscillator are insuflicient to bringthe potential substantially up to the curved part of the characteristic.During the spacing interval, therefore, the 800 cycle frequency will notbe vheard in the receiver lli. It will be understood that properadjustment of the potential difference between the grids and laments Dand M may be made by potentiometers 25 and 26, respectively.

During the marking interval, on the other hand, the high frequencyoscillations superposed upon the normal potential of the grid of thedetector tube D cause a current wave to flow through the output circuitof thc tube, this wave corresponding to the original. marking signalwave at the transmitter. This current wave flows through the resistance12 so that a material IR drop is present across the terminals vofsaidresistance. This IR drop is in such a direction that it is series.aiding with respect to the potential of the C amplifier tube LFAbecomes much more negative with respect to its lilament than during thespacing interval. The current flowing in the output circuit duc to thehal.- tery 17 is therefore reduced. The reduction in the current flowingthrough the resistaum 15 makes the it drop across the terminals of thisresistance small. As shown in thc. diagram, the C battery 1S is so polcdas lo tend to make the grid po il' the potential of the grid dependedentirely upon this baltcry. The llt drop through thc rcsirtain-c 15, onthe other hand, is in such a direction as to ma te the grid of themodulator tube N negative, and the algebraic snm of thc lwo potentialsis such that during the spacing interval the grid will he substantiallyncgzi- 'tive as already stated. lVhcn the .llt drop through theresistance l5 is reduced, hon'- ever, the grid becomes less negativo solhul the tubo lvl now operates upon the curved part of itslcharacteristic andA currcnt can flow in its output circuit. Consequentlythe audible frequency from the oscillator O impressed upon the grid willproduce a corresponding frequency wave through the rcceiver ll so thatan audible tone of, say, S00 cycles is heard during the markingii'itcrval. t will be apparent from the above de scription of theoperation that the low l'rc quency amplilicr l/F is ncccssary in ordcito make the change in the voltage drop across the resist-ance l5 of themodulator lube of the proper direction. lf the output circuit of thedetector l) were connected through the low-pass lilter LPF directly lothc, modulaiing tube through thc coupling of thc resistance 15, J:hecflcct of the marking signal would be to increase the drop through theresistance l5, and therefore makc lhc grid of the modulator even morenegativo than during the spacing interval,v with the result that nocurrent would low in thc output circuit of the modulator either duringthe spacing interval or the marking interval. The interposition of theamplifier lll, however, reversesI the situation so that thc drop throughthe resistance 11 is decreased during the marking interval with respectto thc drop during the spacing interval, and conscquently the audibletone can hc heard in thc receiver during the marking interva Thelow-pass iiltcr ln'll? in the detector circuit is so designed that. itwill pass all signals from zero up lo the maximum iclcgrailih speedwhich ordinarily is of the order oi' lll() cycles. The marking impulsewhich 'lows in the output circuit of thc dcccl'or D in response to thehigh frequency unu'king oscillations will contain all of the frequencycomponents of the original telegraph wave. and ther-:c components willpass through thc filter so that thc impulse which is amplilicd willcorrespond substantiallv lo thc original telegraph wave.

tlll

lill

lllll lllf.

Inter-lering high `frecniency Waves, Whether due to sialic or tointerferingstations, when" where 'li-ein Zero le e lreiiuiencycerresnoudi ug;

te 'the liinil` oil: eudiliility which may he in lire neighborhood oil"20,000 cycles. lhe low- ]iines liller Llull?? lu'iwcver, culsi olii :illdifferencelrequencies allieve l0() cycles, so hnl'.

inerlfcrcnce are entirely Without A cl'lecl. lllren `where iniicrieringwaves heult with ciu-,h olher 'lo produry :i 'lreqneilcy within 'lihcrange ol the liller the heet note is oil? negligihle ell'ecl unless ilyie oli euch nizigniiude :is lio cruise mi. :ipprecielile currinl' waivelo llew .in the output circuit oil? lthe fflcleclor lf), which wculdnel', ordinarily he the cese for usually lzhc .inleril'crence ieeleninller nninlilzuelc Jrhein the desired sig-ruil. lllowever.) .i heetnolzc resulting frein the interaction oi" nn inlerler ing; waive Williihe relatively inuch stronger signal v'zrve inigl'ii, if Within therange oli `the lillzcr, he or" considerable in'iignilxude.

ln general7 Ylilierelere7 Suclr inlerilference :is is heard in "l'hcreceiver only` occurs,` if et all, duringl lhe innrli'ing interval, undnely during;l lhe sourcing; inl'er er] The; eilleclof the ,interferenceVupon lhe im: ol the lieteneili conecquenljly does nel', detract from heintelligihilizy of' the siggnzil.

lili irre well known faifzlwlzlizlt'lzhc cllicicncy olf :i de'tccor or ninodulziiior ove' range is; roughly proportional ilo the Square el" liheinput Willzuidfe7 because the electire dc-lrcl'ed coinliienent arisesfrom lhe Second power `n1 olil the Fourier Se 'ies in accordf :nice n iwhich luhc output Wave may he expressed. Ae there are two tubes in lnhecircuit (the dezeclzor D end the inodulailor lil) having nen-linearcharacteristics, ihe rulzio ci linail signaling; currenll lo interferingcurrcnls will he much greater 'lvhini .in the ence eli' n helerodynereceiver. 'lhie will, oi' course. have lhc eliccl; of ziccenlilmline;`the slironfr signale in (^o11i} nnieon with week SigH nails.Uonseruiently, as the desired signal is ordinarily much Strongri-ir thaninterfering Signals; lhe el'ilccl'I upon 'lihc receiver will he suchlhzil l'here is considerable dieci-unirmiiion against inici ,rence. lnolher Words, ihe :signal lo initier-ference r: i110 1e much hy thehelerodyneiuelihod ae many ufr 5 or i een l.:

n, certain i Y (when the dislnn oper: ler hize hie liey open) i'iher'ein no sliiflic or oliller iiiterlicrence ivlii-z'l'l ic audible.

All', has n so heen iileund lfiuiiz in pruriiici-i no diliiculiiy isencouuileird in nuiinlnining consimili; the l'requency el lille iene lolie licnrd Vin ilie rm'ei'vl'rrj fouillis: linie ie produced by e lovv:lirequeucy oi-iciilzilier. lillence e. conezirlerzihie lnnreniiiiureci: 'lfreigiufnry v:i riuliion would onlir elmnn'e lhe lone n. leu" l ccyelee per second. lilhen i i-leiwznlyue .eyel'ein. il; einrlejjuulvhowever, inirlufulnrly i'lf ille lrequencieai ure verf,7 high. u, #Unullpervnrinlion in lshe hc'gerodyne lire (lueur-V inzij.' chance lille heulnella i'roruone liliul; is uiullihlc lo one l'lzzflz 'e inaudible. lhccirruil; oi ljiile nrescnln inrenl'iion oliV viously eliini'niilei: thi`dillirullxy und een llwrelore he employed zu; well Vlor ,ehorlx i 'uvelengglgh reception zu; l'nr lenig' were leugfilis.

lliufill lie obvious` lhnl;` lille generali prin` ciples hereindisclosed muy he embodied in runny ohcr orijnnirmlions 'Widelydi'llrrenl i'roni those illueirnicd willioul'y depurl'iiu :ifroin lilieSpirit `olf' the invention :us4 deiincd in l'he lfollowing claims.

Villen; is cleinied ie: l. 'llle Incl-hed of rudio delecliioir whichcomprises; de'leeling llroin lille received rzuliio were low frequencycurren; pulsiee corre Spending to telegraph uignzils, suppressing;lron'i :sind puiser; 'lreiniency compeneule1 higher lhiin *chosecerieniziiil lo ordinary l'clen gre/ph "crnusiniueioiu enulinilieuelygenernlxiiu); :in audible. were ofenhslainliiilly conf-Leur amplitude'For iriinei"iesiion lo :i riicei'vcr., :and controllinglzhc linnn @eineci" lille :uulihlc were in uccordzuue vih seid dclceieil und.s-ieleclted curreni'; iinpuluee.

2. ln n indio receiving; eyelein. :i dclicior floriler-walling lfroinl'hc reii'eii'ml rudio were current impulses cori"eupondinu` le lilleeriA inul eiiggunfl, menne lo conluinuormly generale Wares; or ululihleYFrequency sind einheimilnizilly coneslnnl'l ampliindiar u, recelver` :inuululzilmr :lor ecnlrollinp' lille iriuisanieeien oilt :incid :uidihlewere@ 'lo .Quid rec rr. ineime lio prcrent the linneuiisuion ei Huid:uulihle wim/eri through uuid nieduiul'er in ille imienrc oi3 delccl'edsienzil impulser-s, und lucene lo imprese Seid rh .cried wnvcii uponeziid inoifluletor to linen-hy conlrol the l'vrzuufnimsinu ofthe audiblewere lo die receiver in :1ccori'lzuice will) the ruggruil.

S5. ln n rudio receiving uva-riem, n`

d e ljec lior lill] for detecting from the received radio wave currentsof wave form and shape corresponding to the original signal, amodulator, means for continuously supplying audible oscillations ofsubstantially constant amplitude to said modulator, means to prevent thetransmission of said audlible oscillations Y through said modulator inthe absence of detected signal impulses, means to supply said detectedwaves to said modulator to produce m the output thereott wavescorresponding to said audible oscillations but modulated in accordancewith said detected signal Waves, and a receiving circuit associated Withthe output of said modulator to receiveV said modulated waves.

4. In a radio receiving system, a detector for detecting from thereceived radio Waves current waves corresponding to the original signalwaves, means to suppress from said detected waves all of the frequencycomponents higher tliantliose essential to the CJD intelligibletransmission of the original signal, a modulator, means tocoi-itinuously impress audible oscillations o'li substantially constantamplitude upon said modulator, means to prevent the transmission oftsaid audible oscillations through said modulator in the absence ofdetected signal impulses, means to supply said detected waves to saidmodulator'to produce in the output thereot Waves corresponding to saidaudible oscillations but modulated in accordance with y said detectedand selected signal waves, and

a receiving circuit associated with the output oi said modulator toreceive said modulated Waves.

`5. In a radio telegraph receiving system, a detector for detecting fromthe received radio waves impulses of current separated by Zero currentintervals, a modulator, means to continuously :impress audibleoscillations of substantially constant amplitude upon said modulator,means to prevent the transmission et said audible waves through saidmodulator in the absence olf detected v signal impulses, a receiverconnected With said modulator, and means to supply from said detector tosaid modulator detected current impulses separated by zero currentintervals, to control the transmission of audible oscillations from themodulator to said receiver in accordance with the detected currentpulses separated by zero current intervals.

6. In a radio receiving system, means for receiving radio oscillationscontrolled in groups to correspond to marking and spacing intervals, adetector upon which -said oscillations may be impressed, means to biasvthe input of said detector so that during one Vpulse of currentdoes'llow, a modulator,

means to continuously impress audible oscillations of substantiallyconstant amplitude upon said modulator, means connected with saiddetector to impress detected current pulses separated by Zeroy currentintervals upon said modulator, and means to prevent the transmission ofsaid audible oscillations through said modulator during no currentintervals, whereby during a no current interval none of the oscillationsimpressed upon said modulator will be transmitted thorothrough whileduring a current flow interval said oscillations will be transmitted inaccordance with. said pulse olf current.

7. In a radio receiving system, a vacuum tube detector for detectingcurrents corresponding to the original signals, a low 'lirequency vacuumtube amplifier, means to couple the output circuit of said detector lothe input circuit of said amplifier comprising a resistance whosevoltage drop defermines the grid potential ol the amplifier, a vacuumtube modulator, means to impress oscillations upon the circuit olE saidmodulater, and means to couple the output circuit ot said amplifier tothe input circuit of said modulator comprising a resistance whosevolt-age drop determines the potential of the grid of said modulator. i

S. In a radio receiving system, a vacuum tube detector for detectingcurrents corresponding to the original signals, a low frequency vacuumtube amplifier, means lo couple the output circuit of said detector tothe input circuit of said amplifier comprising a resistance whose dropdetermines the grid potential of the amplifier, a filter associated withsaid detector for suppressing from the detected. currents conumnentshaving a frequency higher than those essential to the transmission ofthe original signal, a vacuum tube modulator, means to impressoscillations upon the circuit of said modulator,and means to couple theoutput circuit of said amplifier to the input circuit ot said modulatorcomprising a resistance whose drop determines the potential ot the gridot said modulator.

9. In a transmission system, a plurality et vacuum tubes arranged intandem and each having a grid-filament circuit and a platefilamentcircuit, means to couple the plateilament circuit of any preceding tubein the series to the grid-filament circuit oit the succeeding tube inthe series, said coupling means comprising a resistance wl'iose drop dueto current flowing in said plate-filament circuit determines the biasingpotential` oi" the grid of said succeeding tube, and means to apply abiasing potential to the grid of? the succeeding tube imlependently ofthe biasing potential produced by said plate filament current.

l0. In a transmission system, a plurality of vacuum tubes arranged intandem and loll each having' a grid-filament circuit and aplate-filament circuit, a conductive plate to grid connection from theplate of any preceding` tube el the series to the grid of the succeedingtube of the series, said connection .including a plate current source, afilament to filament connection between the filaments of any twoadjacent tubes, a resistance bridged between said plate to gridconnection and said filament to filament connection, the drop throughsaid resistance due to the flow et current in said plate-filamentcircuit determining the biasing' potential of the grid cit thesucceeding tube, and means to apply a biasing potential to the grid ofthe succeeding' tube independently ont the biasing` potential producedby said plate lilament current.

In testimony whereof, I have signed my name to this specification this21st day of February 1925.

` ALLAN VEAVER.

In testimony whereof, l have signed my name to this specilication this9th day of February7 1925.

FAY HAROLD CHASE.

